A benign syndrome of periodic fever, aphthous ulcer, pharyngitis, and cervical adenitis in children is mediated by inappropriate release of interleukin 12, causing activation of a unique subset of CD3+, CD16+ T- cells with large granular lymphocyte morphology. These cells may be the primary source of interferon, which may be responsible for the clinical manifestation of the attacks. This study will continue to evaluate the plasma concentration of IL-12 and IFN during febrile episodes and correlate the presence of these cytokines.